The electrohydrodynamic (EHD) technology is one that employs a set of electrodes to generate an electric field with high voltage and low current so as to provide a fluid in the electric field with negative charge. The EHD technology is currently applied to, for example, a heat exchanger or inkjet printer. In a conventional heat exchanger a set of electrodes is disposed within a heat-exchanging fluid with low conductivity, such as CFC or equivalent refrigerant, to produce an electric field with high voltage and low current. The electric field will result in a driving force against the heat-exchanging fluid, causing the heat-exchanging fluid to be stirred to thereby increase the heat transfer efficiency of the heat-exchanging fluid.
FIG. 1 illustrates s schematic view of refrigeration cycle of a conventional refrigeration system. The refrigeration system is generally composed of a compressor 1, a condenser 2, an expansion valve 3 and an evaporator 4. In the refrigeration a low pressure, low temperature vapor refrigerant, after being compressed to a high pressure, high temperature vapor refrigerant by the compressor 1, is cooled down to a high pressure, medium temperature state in the condenser 2. Then the pressure of the high pressure, medium temperature liquid refrigerant is lowered by the expansion valve 3 to become a low pressure, medium temperature liquid refrigerator. As the liquid refrigerant from the expansion valve 3 flows through the evaporator 4 and receives heat from the ambient, the liquid refrigerator will be evaporated to become a low pressure, low temperature vapor refrigerant to complete a refrigeration cycle.
The evaporator 4 usually includes a curved continuous copper pipe that allows the refrigerant to flow inside the pipe. A number of fins are intensively arranged on the outer wall of the pipe in order to increase the heat conductive areas for the refrigerant. Also, a fan device is provided to drive air to flow through air-flowing channels formed among the fins, so that the heat exchange can occur with the air. As the temperature of the evaporator is kept low, the moisture contained in the air will be condensed on the surfaces of the fins. The water condensed from the moisture on the surfaces of the fins will then drip down to the bottom of the fins due to gravity, allowing it to be expelled from the fins.
However, the water condensed on the surfaces of the fins decreases the heat transfer areas provided by the fins so that the heat transfer efficiency of the fins is deteriorated. In order to prevent the heat transfer efficiency of the fins from deterioration, the water condensed on the surfaces of the fins has to be removed from the surfaces of the fins as fast as possible. Nevertheless, the removal of water from the surfaces of the fins of the conventional evaporator is relatively slow and time-consuming for the reason that the dripping process of water condensed on the surfaces of the fins is dependent on the gravity of the water. As a result, the removal of water from a conventional evaporator is always not efficiently performed, causing the heat transfer efficiency to be adversely affected.